Perhaps you could check out how people with learning disorders such as dyslexia function. When dealing with people of the sort, there is a certain process related to memorizing words and images, to ensure the correct orthography. Picture-word relationships are quite important in order to learn a new language, and our usually done with the help of flashcards, as mentioned above. However, adults might find the use of flashcards to ridicule them, and hence lower their self-accomplishment feeling since they will feel like a child. A good way to work with adults is often with movies or simple video clips. With these tools, it is easier to associate an image, a word, and a concept altogether, by recalling on a visual aid in their mind.